A Deeper View

The Remotely Operated Vehicle
(ROV) is an underwater robot that helps serve as a scientist’s eyes and hands
in otherwise inaccessible waters. The ROV is equipped with video cameras and lights
and has a manipulator arm that can be used to grab various instruments for
collecting organisms. It has a sonar system that helps the ROV driver see in
low visibility waters, as well as sensors to measure temperature, salinity, and
oxygen. The ROV transmits real-time images through a cable connected to a
control room on the ship. This affords scientists the opportunity to stop and
make observations when we come across an animal of particular interest.

My fellow Scripps Institution of Oceanography student scientist, Mike
Navarro, studies the distribution of squid egg beds in relation to
environmental variables. For much of his fieldwork, Mike uses SCUBA to observe
and collect squid egg capsules. Many scientists and fisherman think that there
may also be squid egg beds in water too deep to be reached by conventional
diving. By surveying the seafloor with the ROV to depths of up to 400 m, Mike
will be able to safely search for deep egg beds. These seafloor surveys will additionally
allow us to make observations on habitat ranges of a number of commercially
important species that dwell on the seafloor. In the case that eggs or animals
of interest are found, we can even collect the organisms alive and bring them
back to the ship’s lab for further study.

My own research is focused on a
community of animals that live in deep open ocean waters, specifically the mesopelagic
zone, which ranges from from 200-1000m (600-3000 ft). The animals that live there include lanternfish
(myctophids), dragonfish, krill, and a number of gelatinous organisms like
jellyfish.

Thus far, I have used midwater trawls for direct collection
and a scientific echosounder for remote sensing to sample the community. The echosounder
works by sending out a sound wave through the water column at a specific
frequency.The sound is reflected
by anything with a different density than the surrounding water, which includes
the seafloor, but also animals. The strength of the reflection can be used to
roughly interpret the types of animals that are living in the water. The
echosounder is useful because it can be run during an entire cruise without
interfering with normal operations, thus allowing me to survey a huge swath of
ocean. However, it is hard to interpret what animals are in the water. I
generally use net collections to help me interpret the acoustic signal. The net
is good at catching fish and other hard-bodied organisms, but many of the delicate
gelatinous organisms are not well sampled by the net tow, because they can fall
apart. A prime example of this is the siphonophore.

Siphonophores are colonial
organisms made up of individual zooids living in a long chain. The colonies often
fall apart in the nets, and much of the animal can be lost through the mesh. Since
siphonopores have high acoustic reflectance, it is important for my research to
get an accurate count of the number of siphonophores that are in the water. ROV surveys can serve as a complement to
acoustic and net sampling, and provide a more accurate picture of what is in
the water column.

Further, when animals are
collected by net and taken out of their immediate environment, they do not
survive well. Observations made by an ROV allow us to observe the animals’
natural behaviors in their own home, which can inform us as to how the animal
eats, moves, interacts with other animals, and much more that we can not learn
outside of their natural habitat.

Finally, ROVs are not only good for
biological observations, but also observations of the seafloor itself. A
research group onboard the San Diego Coastal Expedition is searching for methane seeps, and will use the ROV to
explore potential seep locations (more on methane seeps to come in a few days).
We are extremely excited to explore the waters off of San Diego with the ROV in
the upcoming days!

--Amanda Netburn, Scripps Graduate Student

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San Diego Coastal Expedition, led by Scripps Institution of Oceanography students, is supported by the UC Ship Funds Program